Bizarre claim: Climate Change will poison Monarch Butterflies

On the surface, this looks like some bad science from a couple of green undergraduates who are so eager to save the planet, they’ve lost track of what science actually is. Or, maybe they were never taught. Basically, what they did is create extreme conditions that would never exist in nature, and call it science. From LOUISIANA STATE UNIVERSITY.

It’s an ecological trap

Global warming can turn monarch butterflies’ favorite food into poison

LSU researchers have discovered a new relationship between climate change, monarch butterflies and milkweed plants. It turns out that warming temperatures don’t just affect the monarch, Danaus plexippus, directly, but also affect this butterfly by potentially turning its favorite plant food into a poison.

Bret Elderd, associate professor in the LSU Department of Biological Sciences, and Matthew Faldyn, a Ph.D. student in Elderd’s lab from Katy, Texas, published their findings today with coauthor Mark Hunter of the Department of Ecology and Evolutionary Biology and School of Natural Resources and Environment at the University of Michigan. This study is published in Ecology, a leading journal in this field.

“A lot of global climate change research focuses on a single species, and how that species will be affected by climate change,” Elderd said. “But we know that in reality, species interact, and they are often tightly linked together.”

One such species interaction is that of the monarch butterfly and the milkweed plant, genus Asclepias. The monarch is an obligate feeder on milkweed. Individuals always lay their eggs on a milkweed plant, and the larvae only develop on various species of this particular plant.

“We wanted to explore how species interactions, like that of the monarch and the milkweed, change with climate change, or the indirect effect of climate change on monarch butterflies through the plants they eat and lay their eggs on,” Elderd said.

Faldyn and Elderd found that the local warming associated with climate change can produce chemical changes in milkweed that in turn affect monarch butterflies when they and their larvae feed on certain species of this plant, particularly the non-native milkweed, Asclepias curassavica.

“It’s important to understand how changes mediated through milkweed impact monarch butterflies,” Faldyn said.

There are several different species of milkweed, but they all share a common trait. They produce toxic chemicals in their leaf tissue called cardenolides that deter most vertebrate predators. These chemicals are in the class of cardiac glycosides that interfere with sodium potassium-pumps in the heart and other tissues, and can even affect humans if ingested in large quantities. Monarchs, however, have evolved to become cardenolide-tolerant up to a certain point. By laying their eggs on milkweed plants that contain levels of cardenolides that are toxic for their predators, monarchs protect their caterpillar offspring from being eaten. After hatching and chowing down on milkweed leaves, the caterpillars are full of cardenolides that make them taste nasty to most predators, such as birds. Monarch butterflies also sequester this compound in their wings. Their contrasting bright orange and black wings signal “do not eat me” to birds such as blue jays.

Two monarch butterflies, reared by Matthew Faldyn, feeding on a benchtop in the Elderd Lab at the LSU Department of Biological Sciences. CREDIT LSU

But if a milkweed plant produces too much of this toxic chemical, caterpillars that feed on the plant’s leaf tissue may inadvertently poison themselves.

“It’s a Goldilocks situation for monarch butterflies. Too few of these chemicals in the milkweed, and the plant won’t protect monarch caterpillars from being eating,” Elderd said. “But too high of a concentration of these chemicals can also hurt the monarchs, slowing caterpillar development and decreasing survival.”

The trick lies in monarchs finding a milkweed species that is just right in terms of the amount of cardenolides it produces. In the southern U.S., this ideal species turns out to be the invasive milkweed A. curassavica, as known as “tropical milkweed,” which is commonly sold in gardening stores.

A. curassavica is hardy. It holds onto its leaves longer than most other species, and it flowers throughout the year making it attractive to gardeners and homeowners,” Faldyn said. The plant is often sold to homeowners with a catchphrase such as, “Beautify your Yard, Save the Butterflies.”

And monarchs do love the invasive A. curassavica. In fact, under current climatic conditions, adult monarchs that feed on this species of milkweed demonstrate a higher survival rate and weight. That’s because A. curassavica contains the perfect amount of cardenolides – just on the edge of too much. But environmental conditions that increase cardenolide levels in this plant, such as warmer temperatures, can set up an ecological trap for monarchs.

As this plant senses rising temperatures, it produces more cardenolides, perhaps as a defense mechanism.

Temperature-dependent increases in cardenolide concentrations in A. curassavica, which Elderd and Faldyn observed in the field within three days of placing tiny greenhouse-like structures around these plants, push monarchs over a tipping point, poisoning their larvae, delaying larval growth and leading to butterflies with stunted forewing length.

LSU scientists constructed small greenhouse-like structures, known as open-top chambers, around milkweed plants that increased temperatures to a point that caused the plants to become toxic to monarch butterflies. CREDIT LSU

In essence, with climate change, too much of a good thing becomes a bad thing, specifically when it comes to the tropical milkweed plant. The native A. incarnata milkweed naturally produces fewer toxic chemicals than the tropical milkweed, but warmer conditions don’t radically change these levels. Under conditions of global warming, monarchs feeding on the non-native milkweed fare much worse in terms of growth and survival than monarchs feeding on native milkweed.

“If I’m a monarch butterfly, and I’m responding to past environmental conditions, I’ll lay my eggs on A. curassavica,” Elderd said. “But under conditions of global warming, I’ll be doing my offspring a disservice without knowing it.”

The warming conditions Elderd and Faldyn applied to milkweed plants in the field mimic temperatures projected to occur in Baton Rouge, La. within the next 40 years or sooner. If for example, there’s a heat wave.

“It has become increasingly recognized that species interactions, especially interactions between tightly-linked species, need to be considered when trying to understand the full impacts of climate change on ecological dynamics,” wrote the authors.

Unfortunately, invasive milkweed plants are everywhere throughout the southern U.S. Faldyn hopes to raise awareness among plant sellers, gardeners and home owners that given global climate change, it’s better to plant the native milkweed rather than the pervasive, non-native tropical milkweed plant for the monarchs.

What’s next?

Faldyn and Elderd are involving undergraduate students at LSU in follow-up research, for example to evaluate conditions that might bolster native milkweed plants in areas where they have to compete with invasive species.


Oddly, the Paper they cite in the LSU press release is nowhere to be found as of this writing. Perhaps that is for the best.

82 thoughts on “Bizarre claim: Climate Change will poison Monarch Butterflies

    • I’m not really sure what their conclusions should be. They’re basing this rubbish on a warming world, but strangely their brethren blame more snow and colder conditions on warming as well. I’d like them to first answer how warming is the culprit of cooling and, how through this mechanism their butterflies could possibly suffer from warm milkweed.
      Maybe they should just eat the butterflies since they’re likely against beef as well. I hear they taste as good as dolphins and minke whales, which go very well with some grated puffin and melted cheese.

  1. Both the Monarch Butterfly and Milkweed survived the ice age, as well as every Warm Period since the height of the Holocene warming. Sounds like too many young graduates having to publish, or perish.

  2. Would have to review the paper, of course, but many questions come to mind regarding their methodology, particularly what temperature profile was used to test their hypothesis.

      • Well, considering that summers in milkweed country haven’t been overly hot and just the winters have been warming through this climate change debacle, You’ll need something to trap the heat and simulate the phantom future threat.
        If everybody would put their set-aside ground into bee and butterfly (of all kinds) supporting flora, there would be increases in the local populations. The fact that most of their habitat is along roadsides is their biggest threat of local depopulation by far.

      • They have already downsized after their attempt to examine the effect of warming on Polar Bears with larger greenhouses didn’t go so well. Memorial services to be announced.

  3. Butterflies are smart enough to choose invasive milkweed (man introduced) because of positive traits.
    Won’t the butterflies also be smart enough not to choose the invasive milkweed should its traits turn negative?

    • They probably feed based on the maximum amount of the alkaloid they have in their system. Evolution has a few billion years of trial and error on its side there. They would no doubt switch to something with lower-but just right- toxicity.

  4. Of course the Monach butterflies would not be able to adapt to a gradual increase in toxin levels over 40 years.
    Give these guys a Nobel prize for disproving Darwin.
    Better still give these morons a Darwin prize.

    • Better still give these morons a Darwin prize.

      That is not how it works. They have to remove themselves from the gene pool to get nominated. Then it is a very tough competition.
      But, given the level of intelligence demonstrated, maybe we will not have to wait too long before nomination time.
      Darwin *almost* had it right.
      He said “Survival of the fittest”
      How it really works is: Death to the stupidest!

  5. The moral is, don’t put greenhouse-like structures around the tropical milkweed plants, because it can poison the monarchs. We like monarchs, so don’t do that. Good to know.

  6. How the hell did life survive on Earth for billions of years, if animals apparently can’t survive or adapt to anything?

    • Because humans are causing catastrophic change much faster. In previous times, change happened slower, like meteor strikes, for example. A meteor strike would change things in 500 mili. Seconds. But humans do things much faster than that

  7. Global temperatures have increased approximately 0.1*C / decade over the past century. And that has been weighted more towards the Arctic regions and more toward warmer nights, and less frigid winters. There is nothing about this that could not be remedied by flying another few miles further North in their migration. Insects are hardy. Butterflies are beautiful, but that does not reduce their phenomenal ability to overcome threats in sufficient numbers to reproduce and propagate the species. They are far more threatened by the cold than by warmer temperature.
    What comes next. Microwaving puppies to show how threatened they are by 0.1*/ decade ???

  8. It should be easier to switch from planting tropical invasive milkweed species to planting native species than
    to change the temperature of the planet, no?

    • It should be easier to switch from planting tropical invasive milkweed species …

      Oh come now, you’re using logic and reasoning—two hallmarks of resistance employed by skeptics and conservatives—and will now be resoundingly ridiculed for doing so.

  9. The monarch eats milkweed with its poison for a specific purpose. Because they then contain the poison and suffer no particular effects from it, if a bird eats a monarch it gets sick in a hurry. The birds have thus learned over time that monarchs are not a good lunch at all. This deterrent is so effective that another butterfly (the viceroy butterfly) actually mimics the monarch coloring to cut down on bird predation.
    These guys have a lot to learn about the monarch butterfly.

  10. Considering Milk Weed grows and sustains monarchs in many varied climactic regions, I have a very hard time accepting that small temperature changes can somehow result in poisoning the bugs.

  11. This relentless, taxpayer-funded assault on fossil fuels, nuclear energy and hydropower is going to come to a very bad end. Those pinwheeling monstrosities are only good for doubling or tripling your electric bill and are in-your-face totems to the Enviros and their church of Gaia. Solar and wind for the Southwest may make sense, at times, but what of the rest of the country? If “fossil fuels” are out, then nuclear has to be in.

  12. Hmm.. don’t be too hard on these guys. I can see this as a neat exercise to set your undergrads, to learn about methods, pitfalls and conclusions in designing a science experiment. The association between the Monarch and Milkweed biochemistry is already known, and it is not unreasonable to explore how various temperature regimes might affect the production of the glycosides, and the development of the larvae.
    But, groundbreaking science it obviously is not, and conclusions about the future of this butterfly under climate change cannot possibly be well founded. The Monarch is amongst the most widely distributed butterflies on the planet, is dispersive and adaptive, can tolerate and can reproduce over a wide range of latitude, on several different host species. It Is not a promising target if you want to demonstrate climate ‘damage’. Just framed that way to justify funding, perhaps?

    • If rational criticism was applied to any of these many, many, many ridiculous papers, your comment would have some validity. Also, the entirety of climate “science” would take up a quarter inch of space on a shelf in some University Library near Ross’s Paleontology thesis ( friends reference). The fact that this garbage is actually taken seriously enough to be submitted for review, let alone pass-is a fantastic joke!

  13. No temp numbers, no recognition that Monarchs breed all along their migration range, including much hotter tropical Mexico.
    In otherwords another worthless climate hype fear mongering bit of trash.

    • The numbers involved in that migration are down dramatically, from ~1 billion to ~35 million over the last 20 years.

  14. My guess is that these grad students used A. curassavicea because it is easiest milkweed to grow in Louisiana. Native milkweeds can be tough to grow. At least one of the monarch butterfly sites is upset with the “tropical milkweed” being introduced because it will spread due to global warming even though they admit it is preferred by monarchs. So how exactly are the tropics going to get that much warmer than they are now to cause this supposed increase in toxin in the milkweed?

  15. Let a mining engineer debunk another biology paper. Did anyone spot the fatal flaw? They put the greenhouse apparati around the plants and in 3 DAYS it started killing off and crippling the new butterflies. Has that pasture never endured 3 DAYS of warmer weather than during the experiment? These critters gather and winter around Tampico, Mexcico, halfway down Gulf coast. Does it stay cooler there than at that experimental location? I was in Brownville Texas and Matamoros, Mexico on a hellish hot muggy day a number of decades ago so I think not.
    I can think of a number of other potentially confounding issues depending on the details of the experiment but I’m always hopeful someone like Jim Steele will show up to harpoon this beast of a study

  16. These butterflies have survived the last ice age, the previous interglacial period, the Eemian, which was warmer than this one and periods in the Holocene that were warmer than it is now. The climate change that we are experiencing today is so small that it takes networks of very sophisticated sensors decades to even detect it. Climate change is clealy not a problem that the monarch butterflies face. The real problem they face is the use of pestacides and the distruction of milkweed by humans.

  17. Hmmmm…further reflection indicates,
    the little greenhouses likely roasted the larva.
    This study is all about killing catepillars to scare people.

    • The Greenies want us to start eating more bugs and I suppose they will want us all to cook them in our little easy bake yard ovens. yeeeeeahhh.

      • And of course temperatures then are highly relevant to Monarch butterflies, since they migrate across the US from Mexico to Canada.

      • Keith,
        Apparently you’re unaware that the whole point about Monarchs and milkweed is that they rely on the plants for their multi-generational migration from Mexico to Canada and back, about which I assumed, apparently wrongly, that you knew something.

      • That 1.58% covers most of the Monarch’s range.
        You did realize that this article was about Monarch butterflies? Or were you just trying to distract from the failures of climate science again?

      • Keith Sketchely-
        It is not meaningless. Even on face value the statement covers 1.58% of the Earth! It was also hotter in Canada, which is another 2%.I believe Australia also had drought and high temperatures, as did much of Europe. Nobody knows with any accuracy what Arctic temperatures were so that area should be deducted from total Earth area under consideration.
        I’m thinking we might want to ponder where to place the earth’s ocean surfaces values for the 1930’s since we have virtually no usable data for 70% of the Earth’s surface at that time.
        So I’ll tell you what’s meaningless. It’s any and all claims that the Earth has warmed relative to the 1930’s or 1880’s or any period before that. And I don’t care how many decimal places these unscientific grant hounds go to the right of the decimal!

    • We have the best data base.
      Far from meaningless. Most likely the rest of the world was also warmer.
      The gatekeepers have so cooked the books that we don’t know. But NCAR’s reconstruction in the 1970s showed the 1930s much warmer than NASA and NOAA now pretend it was.

  18. I couldn’t find the article at the link provided but I did find one here by Birnbaum and Abbot Jan 6 titled Insect adaptations toward plant toxins in milkweed–herbivores systems – a review:
    I’d be extremely curious about the temperatures involved as I have grown Asclepias curassavica for few decades in Western Australia and have noticed the Monarchs seem more than comfortable eating them during our hot summer months.
    I’ve also taken temperature readings on some blisteringly hot days and one thing that stands out is while the air temperature may be 43C, readings on the asphalt road may be 65C and off my car a rather warm 83C.. the ground temperature was a lowly 29C, on the grassed areas and the garden beds the highest temperature I could find in direct sun was 26C.
    This may surprise some non-biologists, it surprises some natural history specialists (botanists) that plants can modify their immediate environment .. but a scientist? No, they shouldn’t be surprised – see when a scientist has a theory they take measurements and tests to determine what the facts are. My observations suggest plants transpire more to maintain a cooler temperature on hotter days,
    I’ve not measured the temperature of the individual tiny seedlings growing in ground where temperatures reach 52C, but I think I’m safe to assume their temperature being so tiny would be pretty much the same as the ground but then I have observed them grow to maturation and at some point along the way they alter the local temperatures in line with the above observed measured temperatures.
    As to the butterflies, maybe some of the hotter plants *are* more toxic, but again it may surprise the casual natural historian, these aren’t mindless insensate robots puttering along on a few short lines of code but rather they’re well equipped whole complex organisms which can be seen flitting from plant to plant before deciding which ones deserve their eggs. I’m sure they have chemoreceptors and I’m sure they’re finely tuned to detect which of their offspring’s food will be safest.

    • Your finding will jot be acceptable to science unless you make little tents to cover your observed areas. Ken and Barbie are sold optionally! Sarc?

  19. Washington State has Monarchs, and 3 native Milkweeds.
    Asclepias cryptoceras
    A. fascicularis
    A. speciosa

    All of these are used as a larval host plant.
    It is nice that young people study nature.
    Next: What happens to the Monarchs when the region cools by two degrees?
    Because warming and cooling happen rapidly on a daily and weekly timeframe and slowly on a 40 to 50 year timeframe, these scholars are not learning much. Someday they may learn what they are now missing.

  20. Why didn’t they just put the Monarchs into a microwave and have done with it; then they could have claimed that microwave ovens are also a cause of global warming. Oh wait….

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